I don't know if anyone has run into this problem, but after a few days of testing, I know I'm not totally crazy. For some reason, after updating to Flash 10.1 RC, OS X will not sleep my displays while a flash video is playing. I have no idea why this is happening as I have never had an issue with it before. My setup is as follows: OS X 10.6.3 Firefox 3.6.3 Flash 10.1 RC I know my extensions aren't causing the problem because I'm using the same extensions that I used before this problem started. The only app that might be causing this to happen is Caffeine (running 1.1.1), but again, I used this before with no issues. If anyone can help me figure this out, I would appreciate it. Even if you don't know how to fix it, if you are having a similar problem, post here. If I can't figure out the problem soon, going to submit bug report to Adobe and having multiple claims might help.